Rock Breaking Cartridge and Use Thereof

ABSTRACT

A rock breaking cartridge ( 10 ) which includes a tubular body ( 12 ), spaced inner and outer second caps ( 14  and  16 ) inside the tubular body ( 12 ), a propellant ( 20 ) inside the tubular body ( 12 ) between the caps ( 14  and  16 ), a radially expansible stemming device ( 30 ) inside the tubular body ( 12 ) spaced from the inner cap ( 14 ), and a filler ( 34 ) between the inner cap ( 14 ) and the stemming device ( 30 ).

BACKGROUND OF THE INVENTION

This invention relates generally to the breaking of rock.

As used herein the word “rock” includes rock, ore, coal, concrete andany similar hard mass, whether above ground or underground, which isdifficult to break or fracture. It is to be understood that “rock” is tobe interpreted broadly.

A number of techniques have been developed for the breaking of rockusing non-explosive means. Most non-explosive rock breaking techniquesrely on the generation of high gas pressures to initiate a tensilefracture in rock at the bottom or sides of a relatively short drillhole. Efficient confinement of the gas, produced in the hole, is aprerequisite for ensuring that the available energy is effectively usedto break the rock. In order to confine the gas it is known to make useof stemming, of any appropriate type.

The propellant which is ignited to generate the required gas pressuresis normally provided in a cartridge. The placement of the cartridge in ahole and the positioning of suitable stemming thereafter can betime-consuming and the person doing the work can, as a consequence, beexposed to a dangerous or hostile environment for a relatively longtime.

SUMMARY OF INVENTION

The invention provides a method of using a rock breaking cartridge whichincludes the steps of placing the cartridge in a hole in a body of rockand activating a stemming device which is in or on the cartridge.

The step of activating the stemming device may cause the cartridge to beengaged with a wall of the hole.

The cartridge may include a tubular body and at least a portion of thetubular body may be frictionally engaged with the wall of the hole whenthe stemming device is activated.

The stemming device may be activated on one side by the manualapplication of pressure or force or movement. When a propellant insidethe cartridge is ignited the stemming device may, as a result ofpressure which is generated inside the tubular body, be activated from asecond opposing side.

Although the stemming device may be positioned in or on a componentwhich is attached to the tubular body it is preferred to position thestemming device inside the tubular body.

The method may include the step of weakening the tubular body tofacilitate expansion thereof by the stemming device. The tubular bodymay for example be formed with one or more slots.

The invention also extends to a rock breaking cartridge which includes atubular body, propellant inside the tubular body, and a stemming devicein or on the tubular body.

The stemming device may comprise, at least partly, a device which isknown in the art. However, an important aspect of the invention lies inthe incorporation of the stemming device in the cartridge.

The propellant may be located in an enclosure which is inside thetubular body and the stemming device may be separated from the enclosureat least by suitable filler.

In a variation of the invention the stemming device is formed by a cap,inside the tubular body, which confines the propellant, and by acomponent, also inside the tubular body, with the cap and componenthaving relatively inclined mating surfaces which are relatively movablethereby to cause a portion of the tubular body to expand radially.

The filler may be positioned inside the tubular body between thestemming device and the enclosure.

In a preferred form of the invention the rock breaking cartridgeincludes a tubular body, an enclosure which is defined inside thetubular body by means of first and second caps which are positioned in abore of the tubular body, a propellant inside the enclosure, a stemmingdevice which is positioned inside the tubular body and which, uponactivation, expands a portion of the tubular body in a radial sense, thestemming device being spaced from the enclosure, and a filler inside thetubular body between the enclosure and the stemming device.

The enclosure may be formed by the inner and outer caps and the stemmingdevice may be closer to the inner cap and spaced therefrom. The innercap may be wedge-shaped or conical.

The filler may be positioned between the inner cap and the stemmingdevice and may be of any appropriate kind eg. a particulate materialsuch as sand.

The stemming device may be of any suitable type and may comprise anappropriate device which is known in the art. For example the stemmingdevice may include wedges or components with relatively inclinedsurfaces which are relatively movable thereby to cause a portion of thetubular body in which the stemming device is located to expand radially.

The tubular body may be weakened to facilitate expansion thereof by thestemming device.

The weakening may be done in any appropriate way and for example zonesof weakness may be formed in portions of the tubular body at definedlocations.

The zones of weakness may be defined by grooves or similar formations inthe tubular body but preferably the tubular body is split at least alongone line in a longitudinal sense thereby to define at least one portionof the tubular body which is readily expansible in a radial sense uponactivation of the stemming device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference tothe accompanying drawings in which:

FIG. 1 illustrates a stemming device for use in a rock breakingcartridge according to a first form of the invention;

FIG. 2 shows a rock breaking cartridge which includes the stemmingdevice of FIG. 1, located in a hole in a rock face;

FIGS. 3 and 4 are views corresponding to FIGS. 1 and 2 respectively andshow a different rock breaking cartridge which makes use of a secondtype of stemming device; and

FIG. 5 illustrates how a tubular body used in the rock breakingcartridge of the invention is weakened to facilitate its expansion by astemming device.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2 of the accompanying drawings illustrates a rock breakingcartridge 10 according to a first form of the invention which includesan elongate tubular body 12, inner and outer caps 14 and 16 which arelocated inside a bore 18 of the body, a propellant 20 which is locatedinside an enclosure 22 defined in the bore 18 between the inner andouter caps, a stemming device 30 which is partly positioned inside thebore 18 at an end of the body opposing the cap 16, and a filler 34 whichis positioned inside the body between the inner cap 14 and the stemmingdevice 30.

As used herein “propellant” is to be interpreted broadly to include anyenergetic substance such as a propellant, blasting agent, explosive,gas-evolving substance, or similar means which, once initiated,generates high pressure material typically in gaseous form. “Propellant”does not include a high explosive.

An igniter 36, of known construction, is positioned inside thepropellant 20. An igniter lead wire 40 extends from the propellantthrough a hole 41 in the inner cap and along a groove 42 in an outersurface of the stemming device. A portion 44 of the wire is thereforepositioned externally of the tubular body.

The tubular body is made from any appropriate material such as, forexample, a high density plastics material eg. in an extrusion process.The caps 14 and 16 are made from a similar material for example by usinginjection moulding techniques.

The filler 34 is a particulate material with a high friction capabilityeg. graded sand with an appropriate aggregate or particle size.

The stemming device 30 is shown in further detail in FIG. 1. Thestemming device is made from wood or a suitable plastics material andincludes two wedge components 46 and 48 respectively which have matingsloping faces 50 and 52 respectively. When the wedge components areengaged with each other as is shown in FIG. 2 they form a substantiallycylindrical body which is pressed into position inside the bore 18 ofthe body with a relatively close fit. The wedge component 48 is formedwith the groove 42 in its external surface.

The inner cap 14 is formed with a wedge or conical outer surface 56.

FIG. 5 is a perspective view of an end portion 58 of the tubular body inwhich the stemming device 30 is positioned. This portion is weakened bymeans of a longitudinally extending slot 60 which is cut through a wallof the body for a length which is more or less the same as the length ofthe stemming device and by a second slot 62 which is cutcircumferentially into the body at one end of the slot 60 overapproximately half of the circumference of the body.

FIG. 2 shows the cartridge 10 positioned in a hole 64 formed in a rockface 66. Once the cartridge is correctly positioned the stemming device30 is activated, for example by means of a hammer blow on a large face68 which is presented (in this example) by the wedge component 46. In sodoing the wedge component is driven into the bore 18 with the faces 50and 52 riding over each other. This exerts a radial expansion force onthe portion 58 which, due to the weakening effect of the slots 60 and62, thereupon expands radially outwardly with relative ease. Thecartridge is thereby locked in position with the expanded portion of thetubular body being frictionally engaged with the wall of the hole.

The igniter 36 is ignited in any appropriate way via the igniter leadwire 40 using techniques which are known in the art and which, for thisreason, are not further described herein. Ignition of the propellantresults in the generation of high pressure jet material, substantiallyin gaseous form, in the enclosure 22. Substantial forces are generatedinside the enclosure and the body is radially expanded. Forces areexerted on the caps 14 and 16 which tend to move the caps axially awayfrom each other. The cap 14 is thereby moved deeper into the filler 34and the filler, which is a particulate material with a high frictioncapability, tends to flow towards and against the stemming device. Aforce is thereby exerted, particularly on a large face 70 of the wedgecomponent 48 which faces the filler, which increases the wedging actionof the stemming device. The effectiveness of the stemming device isthereby enhanced by the action of the propellant.

The twin activation of the stemming device, ie. when the stemming deviceis initially manually activated and as a result of the ignition of thepropellant, means that a highly effective stemming action results.

The groove 42 allows the igniter lead wire 40 to pass to a locationoutside the bore 18 and is such that, when the stemming device 30 isactivated, no damage is caused to the igniter lead wire.

FIGS. 3 and 4 illustrate a rock breaking cartridge 10A according to asecond form of the invention. The cartridge 10A is substantially thesame as the cartridge 10 except that the stemming device 30 is replacedby a stemming device 30A. Where applicable like reference numerals areused to designate like components and the following description islargely confined to points of difference between the two stemmingdevices.

The stemming device 30A includes two wedge-shaped components 46A and 48Arespectively which present inclined surfaces 50A and 52A to each otherwhich define a wedge-shaped cavity 74 between them. A wedge-shapedbarrel 76 is positioned in the cavity and a threaded shank 78 is engagedwith a threaded passage 80 in the barrel.

Viewed from one end the wedge components 46A and 48A, when engaged witheach other as is shown in FIG. 3, present an outer surface which has acircular profile and which is slightly less in diameter than thediameter of the hole 64 in the rock face 66.

A washer 82 is fixed to a protruding end 84 of the shank which isprovided with a lever-type formation 86 which facilitates rotation ofthe shank.

The stemming device 30A is engaged with the tubular body 12 of thecartridge as shown in FIG. 4. As is the case with the cartridge 10 shownin FIG. 2 an end portion of the tubular body is weakened in the mannershown in FIG. 5.

Once the cartridge 10A has been positioned in the hole 64 in the rockface the lever formation 86 is rotated in a direction which causes thewedge-shaped barrel 76 to be drawn deeper into the cavity 74. The wedgecomponents 46A and 48A are thereby forced apart and the tubular body isfrictionally locked in position in the hole 64. Once the propellant 20is ignited, pressure exerted by gas, which is evolved by the propellant,drives the inner cap 14 into the particulate filler which is therebyforced into the cavity 74 in the stemming device. The components 46A and48A are urged radially apart with the result that the effectiveness ofthe stemming device is enhanced.

In a variation of the invention the filler is not used. Referring toFIG. 2 the cap 14 does not have the conical surface 56 and an outersurface of its leading end is similar to the wedge component 48. Thewedge component 46 then acts directly on the cap, not via the medium ofa filler. In other respects the cartridge functions generally in amanner similar to what has been described hereinbefore.

The stemming device, in each embodiment of the invention, acts to helpcontain gas, released by the ignited propellant, within the hole in therock face. The high pressure of the gas is effectively contained in thehole 64. The tubular body initially expands plastically confining thehigh pressure material which is released by the propellant and asubstantial force is thereby generated inside the body. As the bodyfractures the energy which is released results in localised fracture ofthe rock in one or more regions adjacent the body.

The invention thus provides a rock breaking cartridge which includes anintegral internal stemming device which may be of any appropriatedesign. The cartridge is inserted in a single operation into a hole in arock face and it is not necessary for a separate stemming device orfiller to be placed in the hole after the cartridge has been positioned.These steps are carried out in one operation. The use of the cartridgeof the invention thus saves time and increases safety because the periodof time required for a person to install the cartridge is reduced.

The rock breaking cartridge of the invention also allows for use to bemade of robotic applications for the insertion process is relativelysimple compared to conventional techniques which require the cartridgeto be placed and then for stemming to be inserted into a hole inseparate operations.

1. (canceled)
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 5. (canceled) 6.(canceled)
 7. (canceled)
 8. A rock breaking cartridge comprising: atubular body, an enclosure which is defined inside the tubular body, apropellant inside the enclosure, a stemming device which is positionedinside the tubular body and which, upon activation, expands a portion ofthe tubular body in a radial sense, the stemming device being spacedfrom the enclosure, and a filler inside the tubular body between theenclosure and the stemming device.
 9. A rock breaking cartridgeaccording to claim 8 wherein the stemming device includes componentswith relatively inclined surfaces which are relatively movable therebyto cause a portion of the tubular body in which the stemming device islocated to expand radially.
 10. A rock breaking cartridge according toclaim 9 wherein the tubular body is weakened to facilitate expansionthereof by the stemming device.
 11. A rock breaking cartridge accordingto claim 10 wherein the tubular body is split at least in a longitudinalsense thereby to define at least one portion of the tubular body whichis readily expansible in a radial sense upon activation of the stemmingdevice.
 12. (canceled)
 13. A rock breaking cartridge according to claim9, further comprising two-wedge-shaped components forming asubstantially cylindrical body which are positioned inside the tubularbody with a relatively close fit with a large face of one componentfacing the filler.
 14. A rock breaking cartridge according to claim 9,wherein the stemming device comprises at least a first component whichdefines a wedge-shaped cavity, a wedge shaped barrel in the cavity and athread mechanism which draws the barrel into the cavity to radiallyexpand the at least first component.
 15. A rock breaking cartridgeaccording to claim 13, wherein one component includes a groove in anouter surface to accommodate a lead wire extending to an igniter in thepropellant.